The polymer showed signals at �� 5.16 for the �CCH group proton of the lactide comonomer, at �� 4.05�C4.13 for the ��-oxy methylene protons of the ��-caprolactone comonomer and at �� 2.3�C2.4 for the selleck chemical protons of the methylene group of ��-caprolactone that is bonded to the carbonyl group. The signals of the caprolactone protons at �� 4.05�C4.13 and at �� 2.3�C2.4 were clearly split into two signals according to the position in the polymer chain. The triplet at �� 4.13 indicated the CH2 group in the ��-caprolactone fragment bonded to an L-lactide unit and the broader multiplet at �� 4.05 indicated the ��-oxy methylene group bonded to another ��-caprolactone unit.37,38 The signal at �� 2.3�C2.4 was split the same way. The triplet at �� 2.4 indicated a group bonded to a L-lactide group and the broader multiplet at �� 2.

3 corresponded to a group that is bonded to another ��-caprolactone group.37,38 The comonomer ratios of the copolymer were calculated as the ratio of the integral of the signal at �� 5.16 to the average integrals of the caprolactone signals at �� 4.05�C4.13 and at �� 2.3�C2.4.38 The 1H NMR analysis showed that the L-lactide to ��-caprolactone ratio was increased from 68/32 of the raw material and the samples of 0 weeks to 76/24 of the PLCL + TCP50 + C at 52 weeks and 71/29 of the PLCL + C at 52 weeks. The results showed a similar effect of the changing of the comonomer ratio of the copolymer as the hydrolysis proceeds, as was seen in our earlier study with similar composites without ciprofloxacin (Ahola et al. Accepted to Journal of Biomaterials Applications).

Jeong et al. have also reported this effect.37 Figure 4. Part of the 1H NMR spectrum of the poly(L-lactide-co-��-caprolactone) raw material. Because the copolymer properties depend not only on the comonomer composition but also on the distribution of the comonomers in the polymer chains, analysis of the microstructure of the polymer was also needed.38,39 The number average sequence lengths of L-lactide and ��-caprolactone were calculated according to Herbert39 and Fern��ndez38 using Equations 2 and 3: (2) (3) where (LA) and (CL) are the molar fractions of the L-lactide and ��-caprolactone comonomers in the copolymer and (LA – CL) is the average dyad relative fraction, which can be calculated from the 1H NMR data of the copolymer. The calculation is well explained in an article by Fern��ndez.

38 Additionally, the randomness factor, R, was calculated using Equation 4. (4) The randomness Brefeldin_A factor is 1 for a random copolymer and 0 for a block copolymer.38 The results of the average sequence length calculations showed that the polymer is rather blocky, R having values of 0.25 for the raw material and the samples prior to in vitro testing. The R factor decreased during degradation of the polymer to 0.18 for PLCL + TCP50 + C to 0.23 for the PLCL + C at 52 weeks indicating that the more random parts of the copolymer degrade first.